The present invention relates generally to testing for color blindness, and more particularly to computerized color vision deficiency testing.
The importance of visually detecting color has increased dramatically with the advent of technology. Color coded computer information, color applications for safety, color comparison test mechanisms, and other needs have created occupational requirements for color vision. As an example, some occupations which now require verified normal color vision include aircraft pilots, dental lab technicians, pharmacists, electricians, lifeguards, and weather analysts. Thus, accurately detecting color deficiencies is important to both individuals working in these fields and those that rely on them to fulfill their duties accurately and safely.
One test commonly used to determine color vision deficiency is the Ishihara color test. The Ishihara color test consists of a number of color plates having a circle of dots of random color and size. Within the circle, some of the dots form a number that is visible to a person with normal color vision, but is invisible to a person having a color deficiency. FIG. 1A depicts an example of a Ishihara color test plate having the number 12 in a different color then the background dots. An outline of the number has been provided for illustrative purposes only. The full test consists of thirty-eight plates.
The Ishihara color test is limited in that it is designed to only detect red-green color deficiency. To determine if a patient also suffers from a blue-yellow vision deficiency a second test must be used. Further, the accuracy of the test depends heavily on the ambient lighting and the condition of the test plates. The test plates are prone to fading and must be kept out of the light except when in use. The test plates can additionally be damaged through contamination, particularly by fingerprints.
Another commonly used test is the HRR test. Unlike the Ishihara test, the HRR it is able to screen for both red-green and blue-yellow vision deficiencies. The HRR test comprises plates having dots of random color and size and includes common shapes as well as patterns that a patient is asked to trace. The first four plates are demonstrative and the next six serve to separate patients with normal color vision from those with a deficiency. The subsequent plates cover all four colors and appear increasingly bold in color to provide a qualitative manner of testing the extent of the color deficiency. FIG. 1B depicts an exemplary HRR plate having a circle and a square in a different color than the background dots. An outline of the shapes has been provided for illustrative purposes only.
Like the Ishihara color test, the accuracy of the HRR test depends heavily on ambient lighting conditions. The HRR test is designed for specific lighting and needs to be performed in a special box to ensure the results are reliable. The condition of the HRR test plates are also a factor in the tests accuracy. The HRR test plates are equally prone to fading and damaged by contamination.
A third commonly used test relies on arranging color chips rather than plates. These tests indicate not only if a patient has a color deficiency but can also provide the type and severity of the vision deficiency. These tests require a patient to arrange a number of color discs according to their similarities, starting from a fixed reference color. Patients with normal color vision will arrange the color chips from blue through green, yellow, orange and red according to the hue circle. However, individuals with color deficiencies will have difficulty with arranging the color chips in the right order and there will be some crossovers in the hue circle, the direction of the cross over indicating the type of colorblindness (i.e., deutan, tritan, or protan). Two common color chips tests are the Farnsworth D-15 and the Farnsworth 100 Hue tests. FIG. 1C illustrates the hue circle of the Farnsworth D-15 test for a person with normal color vision.
The Farnsworth tests are subject to similar limitations as the Ishihara and HRR tests. Accuracy of the test depends heavily on the ambient lighting and the condition of the test chips. To prevent damage through contamination, the Farnsworth tests are sold with gloves for the patient and test administrator to wear and replacement gloves can be purchased at an additional cost. Further, the Farnsworth tests are extremely cumbersome to score. The color chips include numbers on the back to indicate the order they should be placed assuming the patient has normal color vision. Once a patient has taken a Farnsworth test, the test administrator must turn over each color chip and record the numbers on back in the order the patient placed them before the test can be scored. This process is highly time consuming.
Both the Ishihara color test and the HRR test are further limited in that an individual who is repeatedly tested will become familiar with the order of the plates and the correct answers and, therefore, increasing color vision deficiencies may not be recognized. Handling of the plates can also cause degrade their quality, increasing testing inaccuracies. Given the need to trace patterns on some of the plates, the HRR test is especially prone to damage from handling.
All three tests, the Ishihara color test, the HRR test, and the Farnsworth color chips, additionally require a test administrator to conduct the test for the patient and then score it. This consumes valuable time and increases the costs to administer the tests.